Lysine Deficiency in Rats II. Studies with Amino Acid Diets

Abstract

The current availability of an amino acid ration, containing both essential and non-essential amino acids, which will support high rates of growth over long periods of time in young rats, has made possible the study of specific single amino acid deficiencies, uncomplicated by factors introduced through the use of proteins which are inadequate as sources of nitrogen. The picture of lysine deficiency thus created was found not to differ perceptibly from that of lysine deficiency induced by the use of the protein, zein. In addition, this deficiency state was found to be very similar to that induced under circumstances of general protein depletion, with the use of an amino acid ration containing inadequate amounts of all the essential amino acids as well as the non-essential amino acids. Adult rats fed the amino acid diet were found to require small amounts of lysine for the maintenance of body weight. Additional data were gathered in nitrogen balance studies to support previous observations that zein is poorly digested by the growing rat, with large amounts of nitrogen being lost in the feces. An anomalous finding in these studies was the presence of a positive nitrogen balance in animals growing very poorly on the amino acid-fortified zein ration.